Opposed blade air dampers are currently assembled with air diffusers by means of fasteners specially sheet metal screws requiring drilling of the collar wall of the air diffuser and of the outer ends of the strut arms of the air damper and screwing the strut arms to the air diffuser collar with metal screws. This is a cumbersome and time-consuming operation so much so that the axis of the air damper must coincide with the axis of the air diffuser for proper operation of the assembly namely uniform diffusion of the air within the room all around the air diffuser. This, therefore, requires precise location of the holes drilled in the strut arms of the air damper and in the collar of the air diffuser.
U.S. Pat. No. 4,817,508 dated Apr. 4, 1989 entitled "OPPOSED BLADE BALANCED DAMPER", inventor Kenneth PROCHNOW, describes (referring to FIGS. 3 and 4) a system of tabs 44 with pointed ends 46, 48 at the ends of struts 26 which engage a groove in the interior of an air duct 12 to support the damper frame 20. However, in this system, the tabsprongs 44 depend from downwardly extending legs 42 secured to the struts 26 and the points 46, 48 cannot be forced to deform the air duct wall at the bottom of the groove axis coinciding with the axis of the duct 12. It follows that the damper assembly is not positively held within the duct 12 against axial movement and rotation.